So does this mean that AA provided you with a new flight to DC, and that you didn't actually have to pay for a new flight as your first post seemed to suggest?

And were you required to stay overnight in/near Miami, and did AA provide a hotel for you? Or did you find you either had to stay overnight in the airport, or find and pay for your own accommodation?

You don't seem to to realise the significance of the various questions that have been raised. You were there and know exactly what happened; we are trying to piece together the sequence of events based on the very limited details you have provided. Despite several posts, you have glossed completely over the basic information of all the things that happened, and which would help us give you better counsel and/or explain what you should expect and what you could now expect to get from AA; but without the specifics, nobody here can provide you with specific advice or explanations that pertain to the specific set of circumstances you experienced that night (and, apparently, also the following day, given that it appears you must have had to stay overnight in Miami - a very significant fact that so far has not been mentioned by you at all)